10/23/2007

orange!! (the most exciting thing i've seen in a while)

You've seen a lot of the perylene diimides I've made. (In case you missed them, here they are.) To this point, they've all looked the same--red to violet in the solid state. This one is different. It's so tangerine it hurts a little. Also, it isn't a fibrous pancake--all the others give me long, flexible needles, if they crystallize at all (perylenes are infamous for gellating). This one actually behaves like a normal crystalline solid! And it's sparkly! See?



Why orange, though? This is neatly explained by quantum interference effects in a super-cool but somewhat ancient paper by Roald Hoffmann and friends. (Do not fear the theoreticalness, undergrads and synthetikers. It's an easy read--very clearly written. I'd kill to see more like this in the literature.)

I'll say first that the black PDIs they report sound really exotic and I kinda wish mine were that color.[1] One of the more interesting conclusions of the paper is that the dyes with the most substantial band-broadening in the solid state are the ones with the highest photosensitivities. Cool, eh? I won't say too much more about crystallochromy, since the paper discusses it so much more nicely than I could if I tried, so...just read it?[2]

Since--as Kazmaier and Hoffmann state--the color of these compounds depends on their crystal packing, and this derivative is a markedly different color than anything else I've made, I'd KILL to see a structure of it. Of course, crystal growing takes time, so I'll be patient.

Also, keep an eye on CBC. We're planning something REALLY COOL! We just can't tell you what it is yet. ;)

[1] Black is a super awesome color if you're trying to make solar cells. Black with significant near-IR absorption is even better. Black leather with spikes is good for BDSM and death metal.

[2] For another, more recent, nifty paper on dye aggregates, check this out. Someone covered it already. I tried to find their post, but...I read a lot, and I've forgotten who pointed it out. Care to correct my memory?

15 comments:

Mitch said...

Quick, splash some liquid N2 on it. :P

Ψ*Ψ said...

Too late--it'll be in Pennsylvania soon. :)

Mitch said...

Why pennsylvania?

sam said...

why is black good for solar? the black is an artifact of being crystalline, right? in solution, the aborption spectrum would not be broadband. can you use crystals in solar cells?

Ψ*Ψ said...

Mitch: Some engineers want to play with it.
Sam: The materials in our solar cells are solid--crystalline thin films.

sam said...

cool!

Kyle Finchsigmate said...

hehehehe i know!

Ψ*Ψ said...

Yes, Kyle, but we're trusting you to keep the secret. Else, the ninjas will be sent after you. :D

mevans said...

Can't wait to see what you guys have planned! Feel free to actually follow up on it (*cough cough nanocontest *cough cough).

:-)

Excimer said...

Do most PDIs gellate? I mean, that example you have is amphiphilic (sort of), which i would expect to be a gel, but other PDIs?

Uncle Al said...

Make a C2-symmetric dimer of your problem molecule to crystallize near anything. C2 symmetry marvelously lattice packs.

Charge transfer bands offer big epsilons and big red shifts - Creutz-Taube ion, Prussian blue, magnetite and ferrites overall - especially if the resonance contributors approach degeneracy.

Sooo... You make an interal charge-transfer near C2-dimer, or take what duplex works and dimerize that to C2 symmetry. Diploid and Tetraploid Molecular Solar Harvesters. With any luck Prince Charles will get on your case for making Franken-molecules, and you're famous.

Ψ*Ψ said...

Excimer: IDK. Every single one I've made has gellated to some degree--they hold onto solvent like mad.
Uncle Al: EVERYTHING I'm making is C2 symmetric.

mjenks said...

Black leather with spikes is also good for rooting on the Oakland Raiders.

Hap said...

MJenks:

A lobotomy is also good for rooting on the Raiders - maybe even to run them.

Ashutosh said...

do or dye